The high pressure phase transformation behavior of silicon nanowires

Si nanowires of 80–150 nm and 200–250 nm diameter are pressurized up to 22 GPa using a diamond anvil cell. Raman and x-ray diffraction data were collected during both compression and decompression. Electron microscopy images reveal that the nanowires retain a nanowire-like morphology (after high pressure treatment). On compression, dc-Si was observed to persist at pressures up to 19 GPa compared to 11 GPa for bulk-Si. On decompression, the metallic b-Sn phase was found to be more stable for Si nanowires compared with bulk-Si when lowering the pressure and was observed as low as 6 GPa. For the smallest nanowires studied (80–150 nm), predominately a-Si was obtained on decompression, whereas for larger nanowires (200–250 nm), clear evidence for the r8/bc8-Si phase was obtained. We suggest that the small volume of the individual Si nanowires compared with bulk-Si inhibits the nucleation of the r8-Si phase on decompression. This study shows that there is a size dependence in the high pressure behavior of Si nanowires during both compression and decompressionL.Q.H. acknowledges her support from an Australian Government Research Training Program Scholarship. J.E.B. would like to acknowledge funding from the ARC Future Fellowship Scheme. A.L. acknowledges financial support from the Austrian Science Fund (FWF): Project No. P28175- N27 and e-beam lithography support by Manfred Reiche from the Max Planck Institute of Microstructure Physics, Halle, German

FIB Based Micro Fabrication Technique for a Novel Type of Scanning Electrochemical Microscopy Probes

Scanning Electrochemical Microscopy is a powerful technique to obtain in situ information of a wide range of processes occurring at interfaces. However, one major drawback of this technique is the lack of high spatial resolution compared with AFM or STM, due to the interference of the currents originated by the topographical and the electrochemical effects, respectively. Hence, a simultaneous but independent sensing of both, the topographical and the electrochemical information with high spatial resolution is a major issue in the field of scanning electrochemical microscopy (SECM). In this paper, we present a Focused Ion Beam (FIB) based technology, which, for the first time, enables the realization of an independent, simultaneous sensing of both the topography and the electrochemically active interfac

In-doped Sb nanowires grown by MOCVD for high speed phase change memories

We investigated the Phase Change Memory (PCM) capabilities of In-doped Sb nanowires (NWs) with diameters of (20-40) nm, which were self-assembled by Metalorganic Chemical Vapor Deposition (MOCVD) via the vapor-liquid-solid (VLS) mechanism. The PCM behavior of the NWs was proved, and it was shown to have relatively low reset power consumption (~ 400 μW) and fast switching capabilities with respect to standard Ge-Sb-Te based devices. In particular, reversible set and reset switches by voltage pulses as short as 25 ns were demonstrated. The obtained results are useful for understanding the effects of downscaling in PCM devices and for the exploration of innovative PCM architectures and materials

In-doped Sb nanowires grown by MOCVD for high speed phase change memories

We investigated the Phase Change Memory (PCM) capabilities of In-doped Sb nanowires (NWs) with diameters of (20-40) nm, which were self-assembled by Metalorganic Chemical Vapor Deposition (MOCVD) via the vapor-liquid-solid (VLS) mechanism. The PCM behavior of the NWs was proved, and it was shown to have relatively low reset power consumption (~ 400 μW) and fast switching capabilities with respect to standard Ge-Sb-Te based devices. In particular, reversible set and reset switches by voltage pulses as short as 25 ns were demonstrated. The obtained results are useful for understanding the effects of downscaling in PCM devices and for the exploration of innovative PCM architectures and materials. Keywords: Phase change memories, Nanowires, MOCVD, In-Sb, TEM, XR

Electromagnetic enhancement effect on the atomically abrupt heterojunction of Si/InAs heterostructured nanowires

Producción CientíficaSemiconductor nanowires (NWs) present a great number of unique optical properties associated with their reduced dimension and internal structure. NWs are suitable for the fabrication of defect free Si/III-V heterostructures, allowing the combination of the properties of both Si and III-V compounds. We present here a study of the electromagnetic (EM) resonances on the atomically abrupt heterojunction (HJ) of Si/InAs axially heterostructured NWs. We studied the electromagnetic response of Si/InAs heterojunctions sensed by means of micro-Raman spectroscopy. These measurements reveal a high enhancement of the Si Raman signal when the incident laser beam is focused right on the Si/InAs interface. The experimental Raman observations are compared to simulations of finite element methods for the interaction of the focused laser beam with the heterostructured NW. The simulations explain why the enhancement is detected on the Si signal when illuminating the HJ and also provide a physical framework to understand the interaction between the incident EM field and the heterostructured NW. The understanding of this process opens the possibility of controlling the light absorption/scattering on semiconductor NWs with the use of heterostructures while taking advantage of the properties of both Si and III-V semiconductors. This is important not only for current NW based photonic nanodevices, such as light sensors, but also for the design of new optoelectronic devices based on NWsJunta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. Project Nos. VA293U13 and VA081U16)Comisión Interministerial de Ciencia y Tecnología (Proyect CICYT MAT2010-20441-C02)Ministerio de Economía, Industria y Competitividad (Projects No. ENE 2014-56069-C4-4-R

Scanning Capacitance Microscopy Investigations of Focused Ion Beam Damage in Silicon

In this article, we explore the application of Scanning Capacitance Microscopy (SCM) for studying focused ion beam (FIB) induced damage in silicon. We qualitatively determine the technologically important beam shape by measuring the SCM image of FIB processed implantation spots and by comparison of topographical and SCM data. Further, we investigate the question how deep impinging ions generate measurable damage below the silicon surface. For this purpose, trenches were manufactured using FIB and analyzed by SCM in cross sectional geometry

Nanoscale aluminum plasmonic waveguide with monolithically integrated germanium detector

Surface plasmon polaritons have rapidly established themselves as a promising concept for molecular sensing, near-field nanoimaging, and transmission lines for emerging integrated ultracompact photonic circuits. In this letter, we demonstrate a highly compact surface plasmon polariton detector based on an axial metal-semiconductor-metal nanowire heterostructure device. Here, an in-coupled surface plasmon polariton propagates along an aluminum nanowire waveguide joined to a high index germanium segment, which effectively acts as a photoconductor at low bias. Based on this system, we experimentally verify surface plasmon propagation along monocrystalline Al nanowires as thin as 40 nm in diameters. Furthermore, the monolithic integration of plasmon generation, guiding, and detection enables us to examine the bending losses of kinked waveguides. These systematic investigations of ultrathin monocrystalline Al nanowires represent a general platform for the evaluation of nanoscale metal based waveguides for transmission lines of next generation high-speed ultracompact on-chip photonic circuits